Dredging Impact Assessment and Monitoring Services
Dredging Services
- Collection and contaminant testing of sediment cores
- Monitoring contaminant releases at confined disposal facility weirs
- Sediment plume mapping and water quality testing at dredging and disposal sites
- Biological sampling of benthic invertebrates and fish at dredging and disposal sites
- Monitoring ecological effects of beach nourishment and sand removal projects
- Evaluation of potential contaminant exposure pathways caused by dredging
- Essential Fish Habitat assessments of dredged areas
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Versar has been providing dredging planning, impact assessment and monitoring services to the U.S. Army Corps of Engineers and a number of states as well as commercial clients since 1981. We offer a full range of services to assess the environmental and ecological effects of dredging and dredged material placement, as well as to assist clients in planning, beneficial use evaluations, and public outreach. Versar’s project experience with dredging is diverse, and has included projects involving removal and disposal of contaminated and uncontaminated sediments, open water and confined dredged material disposal, beneficial use projects such as wetlands creation and restoration, beach nourishment and restoration, sand mining of offshore borrow sites, and evaluation of artificial reefs as mitigation for shallow water disposal.
Versar first began investigations into the ecological effects of dredging in work performed in the early 1980s for the Maryland Departments of Natural Resources and Environment and the Maryland Port Administration. Versar developed a multi-disciplinary, multi-year program to assess potential effects of placement of material dredged from Baltimore Harbor approach channels in deep holes in the Chesapeake Bay. The project included participation of the Maryland Geological Services and University of Maryland, with project elements including sediment sampling and analysis, benthic, fisheries and water quality assessments, hydrologic and sediment modeling, and presentations at public permit hearings. These early efforts provided the experience and expertise that were the basis for award to Versar of multi-year support contracts from the U.S. Army Corps of Engineers that expanded the scope of services we can provide in this area.
For the Philadelphia District USACE, alone, Versar has conducted more than a dozen delivery orders designed to evaluate sediment contaminant concentrations in support of dredging projects. Versar has conducted more than a dozen delivery orders designed to evaluate sediment contaminant
concentrations in support of dredging projects. Samples for sediment testing typically
are collected using a vibracore to obtain deep (up to 10 foot) cores of the material slated for
dredging. Data obtained from these surveys are compared to sediment guidance values to address the
concerns of resource managers and to obtain the necessary permits to conduct dredging. Versar has
provided a full range of sediment contamination assessment services to help evaluate potential risks
from toxic chemicals. Versar's field testing and analytical services include bulk sediment testing,
elutriate testing, and TCLP testing. Many of our sediment contaminant testing programs have employed
state-of-the-art laboratory techniques to address special concerns of local resources agencies, such as
congener-specific high resolution PCB testing. Versar has conducted extensive soil testing to evaluate
potential human health issues and to assess mobilization of contaminants to groundwater. Because dredged
material is often deposited in upland disposal sites, where it becomes soil after drying, bulk sediment
results are often analyzed as soil and compared to state and federal soil cleanup concentrations.
Versar’s field team collecting vibracore samples in the approach channel of the C&D Canal. Core samples up to ten feet in length are used to characterize contaminant concentrations prior to dredging. In the laboratory, sediment and site water are mixed to conduct the modified elutriate test, which is used to predict concentrations of contaminants that may be released into the water column during dredging operations or from a weir discharge.
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Versar has performed multiple, risk-based analyses to assess potential risks to human health
and the environment from contaminated water, sediment, and soils. Such analyses are conducted
to evaluate potential risks, in accordance with federal and local regulatory guidance. Versar's
risk assessment for individual projects has provided a framework for discussion of potential impacts
from dredging projects, such as mobilization of sediments resulting from dredging and discharge of water
from confined disposal facilities, with regard to regulatory criteria. In addition to providing these
analyses in formal reports, Versar has represented the USACE at regulatory and public meetings to add a
risk-based discussion of contaminant issues.
Versar's staff is widely recognized for expertise in sediment sampling techniques for chemical analyses.
Our experience in sediment sampling is extensive; we have collected hundreds of sediment samples throughout
the Delaware Estuary and near coastal Atlantic. Versar has been widely recognized for expertise in sediment
sampling for many years. Versar developed the prototype sampling program for EPA's EMAP, for which our field
crews conducted sediment sampling for toxicological testing for contaminants such as chlorinated pesticides,
PCBs, PAHs, and inorganics.
Our use of automatic samplers to collect 24-hour composite samples at confined disposal facilities weir discharges saves the costs of mobilizing field teams to conduct the round-the-clock grab sampling required by the water resource agencies. This device also improved the quality of the data by increasing the number of subsamples that were collected in a 24-hour period.
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Versar's experience in chemical analysis of sediments includes a variety of studies and different suites of
analytes. Versar designs sampling and analytical methods to best meet clients' needs, including performing
differential compositing of sediment samples. To evaluate sediment contamination within proposed dredge areas,
Versar has divided samples collected along channels to determine the chemical concentrations within the sediment
to be dredged and composited deeper sediments to predict concentrations of contaminants after dredging is complete.
The interpretation of sediment chemical results is based on ecological risk. Risk assessment is a highly
specialized discipline that requires an understanding of chemistry, toxicology, ecology, and statistics.
Versar’s staff is well versed in sediment studies and includes specialists in all pertinent disciplines. Risk
assessment has proven critical for understanding chemical results frequently during the past several years.
Given the nature of dredging projects in the current political environment, as well as the involvement of public
interest groups and the media, Versar has played an integral role in providing a risk based perspective of chemical
results. Rather than simply producing data tables with little or no interpretation, Versar developed a method for
evaluating ecological and human health risks of a hypothetical dredge project. To prepare an EIS for proposed
deepening of the C&D Canal, Versar developed a conservative scientific approach based on EPA guidance for
Superfund sites to evaluate potential risks from placing dredged material in upland disposal sites.
Versar’s broad experience with ecological effects of dredging was the basis for being awarded a contract from the Delaware Department of Natural Resources and Environmental Control (DNREC) to develop a methodology for evaluation of proposed dredging project in Delaware’s Inland Bays. The document prepared by Versar now serves as the basis for evaluation of all permit applications for dredging in the Inland Bays, and addresses all water quality and ecological issues associated with dredging.
